Vulnerable plaques are lipid filled cavities that form within the wall of an artery.
These plaques, when ruptured, can cause massive clotting in the artery. The resultant clot can interfere with blood flow to the brain, resulting in a stroke, or with blood flow to the coronary arteries, resulting in a heart attack.
To locate vulnerable plaques, one inserts a catheter through the lumen of the artery. The catheter includes a delivery fiber for illuminating a spot on the arterial wall and a collection fiber for collecting scattered light that results from that illumination. The delivery fiber and the collection fiber form distinct optical channels within the catheter. The catheter used for locating plaques is thus a multi-channel catheter.
Light scattered as a result of illumination by the delivery fiber is scattered in many directions, both by structures within the wall of the artery and by particles in the blood. This results in a diffuse glow similar to that one experiences in a dense fog. A very small portion of this scattered light ultimately falls on the face of the collection fiber. The remainder of the scattered light, which may contain useful diagnostic information, is simply wasted. Based upon this miniscule fraction of the total available scattered light, a processor determines whether or not the patient's life is endangered by a vulnerable plaque lurking within the arterial wall.